The present invention relates generally to an improvement in a sheet collator of the type wherein a plurality of sheet storage bins are provided for storing stacks of sheets. In each of these bins, a sheet feeding means is provided to feed individual sheets from each of the bins to a conveyor located adjacent the open end of the bins. The conveyor then delivers the sheets fed from the bins to a discharge station of the collator wherein the desired collation of the individual sheets is completed. A number of sheet feeding devices have been used in such collating apparatus to feed individual sheets from each of the bins. One well known method for feeding the sheets from the bins has been the use of sheet pusher arms which are simultaneously reciprocated in each of the bins to push the top most sheet of the stack in the bins into engagement with the conveyor system.
These sheet pusher arms have taken a number of different configurations all in an effort to improve the sheet feeding capabilities of the collator. These sheet pusher arms generally have a sheet engaging portion at their end which consists of a flat pad or a roller or some other device which physically engages the top most sheet in the bin. When the pusher arms reciprocate, a sheet will be fed out of the bin when the pusher arm is traveling in one direction but it is desired that there be no action between the end of the sheet pusher arm and the sheets in the bin when the sheet pusher arm is traveling in its other direction. To provide this movement, it has been common to use specially shaped pads or rollers having one-way clutches in rollers at the end of the pusher arm to provide this required action.
The specially shaped pads required carefully selected material because the coefficient of friction between the paper and the pad must be closely controlled. In addition, the shape of the pad required close control and often times wear of the pad would change both its shape and its coefficient of friction, thereby introducing sheet feeding problems to the operation of the machine. Likewise, the use of one-way clutches or other specially shaped rollers again proved to have drawbacks due to the operation of small critical parts and the effect of paper dust on the small components of the rollers. One such sheet pusher is shown in U.S. Pat. No. 4,026,538 to Brown et al and which is also assigned to the same assignee of the present invention.
In addition, it was sometimes desired to run a collator with only a portion of the bins being used to feed sheets. For instance, where a ten-page booklet was being collated and a twenty-bin machine was being used, ten of the bins would not be needed in this operation. In the bins that were not being used, the sheet pusher arms would still be reciprocally driven against the bottom of the bin thereby introducing further wear to the sheet engaging components which had been selected to operate on the paper sheets and not on the structure of the bins. Electrical solenoids have been used in some instances to activate and/or deactivate sheet pursher arms not in use. However, such a system of solenoids involves complex linkages and additional electrical components and controls which increases the cost and may hamper the reliability of the machine. Thus many collators would not permit adjustment to deactivate the sheet pusher arms of sheet storage bins not in use and those that do present a number of drawbacks.